Traffic lights have been used since the early 1900's to control vehicular traffic flow by advising drivers when and where to stop, proceed, turn, etc. The growing use of traffic lights attests to their effectiveness in directing traffic flow, reducing the incidence of accidents, and most recently to their utility in controlling the flow of traffic through large metropolitan areas when used in conjunction with computer driven systems.
Interestingly, the modern traffic light is no different today than it was decades ago. The basic light still employs red, yellow, and green filters over incandescent lamps that are sequentially turned on and off by an electromechanical timing switch or by more modern solid state traffic controllers. Recent developments in solid state lamps, i.e. light emitting diodes (L.E.D.) have permitted the replacement of the conventional incandescent-based traffic lights with L.E.D.-based traffic lights. Examples of L.E.D.-based traffic lights can be found in U.S. Pat. Nos. 4,729,076 and 5,136,287. The main advantages of L.E.D.-based traffic lights over an incandescent-based traffic lights are much lower power usage, i.e. higher luminous efficiency, and much longer lamp life. Other than luminous efficiency and lamp life, other important properties of light emitting diodes have not yet been utilized in traffic control systems. The present invention incorporates improvements in traffic light technology made possible by the use of light emitting diodes.